Introduction: Recycled Plastic Keychain

It is difficult to find proper waste management system in Bali, and this has been an issue for generations now with no real solution in place or in site. Dumping and burning are the easiest yet lest sustainable solutions to stop the waste from pilling up.

Everyday Bali produces 4000 tons, and of this total only 4% get recycled. The other 96% end-ups in the landfill, the ocean, or even worse get burned (Bali Partnership Team). In order to help stop the growing waste problem in Bali, the Green School Bali established a recycling and innovation center to educate about waste and viable solutions. Our facility has 21 categories of separation bins and collects more than 1 ton per month of recyclable trash. Most of the trash we deliver to ecoBali, another non profit focused on recycling, and some of it we try to recycle within the school with our 'precious plastic' machines. The recycling project at school run as a learning platform for the students to understand the waste problem in Bali and more importantly develop their creative thinking in how they can turn the plastic pollution into a plastic innovation.


- Clean and Dry Plastic Bottle Caps (HDPE Plastic)

- Acrylic Plastic Mold

- Clamps (2 Pcs)

- Shredding Machine

- Injection Molding Machine

- Container to put the shredded plastic

- Pliers

- Wrench

- Metal Stick to take out the molten plastic from the mold

Step 1: Learn About the Type of Plastic

In order to start any recycling project, it is important to learn about the basic knowledge of plastics. Did you know there are 7 different types of plastic? Different types of plastic have different characteristics which make each type of plastic recycle differently. The type of plastic is easy to identify by looking at the 'code' or a single digit from 1 to 7 surrounded by a triangle of arrows. This symbol was designed by The Society of the Plastics Industry (SPI) in 1988 to help consumers and recyclers to differentiate types of plastics as well as providing a uniform coding system for the manufacturers. The picture attached explain each symbol of the plastic.

Source :



Step 2: Collect the Materials

In this process we will recycle the High Density Polyethylene (HDPE) and the Polypropylene plastic (PP). These should be kept separated because the melting temperatures for each are different, around 180 C for HDPE and around 160 C for PP. You can collect the materials from the nearest recycling center. To differentiate the materials, you can look the number in the middle of the recycle symbol. Number 2 for HDPE, number 5 for PP.

Step 3: Wash and Dry the Materials

Having clean material is important in the recycling process. because it is harder to recycle material that are not clean or dirty. So, what to do? Just simply wash your recyclable plastic from any leftover food and take out the labels. Most of the labels are not the same material as the whole plastic packaging, so its important to remove as much of them as possible.

Step 4: Shred the Plastic With the Shredding Machine

Shredding machine is used to reduce the size and volume of the plastic. It becomes flakes when the plastics come out from the machine. Shredded plastic is much easier to handle and the size fits into the recycling machine (injection molder and extrusion machine). Most importantly the smaller flakes allow for more surface area to be headed, allowing the plastic to heat more evenly and faster. It is also cost-effective for waste management industry because its easier to move around and handle shredded plastic instead of bottles and containers.

Here are the steps :

1. Get your plastics ready

2. Put container underneath the machine to collect the flakes

3. Turn the machine on

4. Push the forward button.

5. Put your plastic in, one by one.

5. If it gets stuck, push the backwards button.

6. The plastic will come out underneath in small flakes

7. Wash again if there are still some impurities

Step 5: Melt the Plastic With Injection Molder

The plastic flakes heated to 200C allow the plastic to melt into usable shaped products, such as a key chain.

How injection molding works?

Before the plastic is heated, we first need to create a mold. In this case we used the laser cutter. The mold is made from acrylic plastic. Acrylic plastic is cheaper than the other mold materials (such as steel, etc). Since we have laser cutter in our facility, it is much easier to create the mold from the acrylic material, which holds it shape under the pressure and wont stick to the melted plastic in the machine.

Here is the process:

1. Put the mold underneath the injection. Look at the picture for the arrangement of the mold

2. Put the plastic into hopper. The plastic could be a form of granule, beads, or flakes.

3. Push the handle down to make the plastic go into the tube. The tube melts the plastic at 200C and the molten plastic goes into the mold cavity. This is when the color of the plastic can mix.

4. Check the molten plastic if it is coming out from the mold. It indicates that the mold is already full with the molten plastic.

5. Wait for 2 minutes for the molten plastic to be cool enough to remove from the machine.

6. Take off the mold from the injection machine.

Injection molding is the most common method of plastic part manufacturing. It’s quick, accurate, involves low labor cost and scrap loss, and can be used with many polymer types. The issue with injection molding is its high initial cost for producing the mold, which can range from hundreds to thousands of dollars (depending on size, sophistication, surface finishes, etc.) (source :

Step 6: Customize Your Keychain

In this example we discussed how to make a keychain but just about any other shape can be made using injection molding. 2D shapes are easier because if the object is too complex you will need to make a 2 part mold which can add to the complexity of the shape and design and is generally more difficult. Once you get the hang of the right temperature and the cooling time, you can then focus on what colors you want to use to make some really nice swirl patterns or color combos. Lastly, drill a hole and add your keychain so you can bring your newly made plastic key chain on the go! Every bit of recycled plastic helps stop it from getting burned or dump in the river so do your part and recycle where you can!